Core material composition, mold core, and process for making mold cores



Patented Nov. 8, 1949 CORE, AND MOLD CODES PROCESS FOR MAKING some s. Adams, Phoenix, Aria.

No Drawing. Application April 8, 1946, Serial No. 660.419

1 This invention pertains to mold cores used in casting aluminum and magnesium, to the process of making such cores, and to a composition from which such cores may be made.

vIn casting the light metals, aluminum and magnesium, it is necessary to provide adequate venting for gases formed as the metal is poured. Where cores are necessary as a part of the mould venting -by the usual means is impractical in some cases and impossible in others. It is highly desirable to dispose of the gases formed as the mold is filled so that the casting will be free from blow holes and will fully conform to'the mold. While the core material must be sufficiently porous to absorb ortransmit gases for venting, it must also be of a texture which will resist the flow of melted metal and present a mold wall impervious to the melt. In addition the core must be friable, and easily broken down for removal after casting.

4 cu (on. era- 1x8) it is baked at a temperature of about 600 degrees In view of the foregoing one of the objects of my invention is to provide a composition of materials which can be easily and quickly mixed with a small amount of water to form a moldable core material which can be hardened and dehydrated by baking at a low, temperature for a short time;

A second object is to provide a composition of materials, as above stated which, after baking, will provide core which will absorb and con-. duct away all gases ordinarily released when pouring molds with light metal such as aluminum or magnesium, and at the same time have a surface which will resist pressure of the melted metal and keep its shape at all times during pourin and A third object is to provide a core made, as above mentioned, which is readily friable after the casting has cooled.

Other objects will appear, hereinafter,

I attain the foregoing objects by the methods and in the manner, hereinafter explained.

First, I make a uniform mixture of expanded Perlite, screened to a uniform size and a binder of natural powdered rosin 11 parts, synthetic urea-formaldehyde resin parts, and ordinary siliceous clay 49 parts, by weight. Preferably these ingredients are mixed in the proportion of 95 to 97 percent perlite and 5 to 3 percent binder. However binder can be added up to percent by volume. The ordinary silicious clay as above referred to is clay containing approximately thirty-four (34) percent S102 and varying quantitles of iron oxide, aluminum, lime and magnesia, approximately 66 percent.

- formation of blow holes or gas Fahrenheit until dehydrated and carbonized. This takes from one half hour to one and onehalf hours, depending on the size of the core. Due to the nature of the perlite no shrinkage takes place.

This core may be surfaced in the usual manner to obtain a smoother finish, if desired, but

is ordinarily ready for use without further finishing when cooled.

After being installed in a mold, and after casting a core made as above described, it may be broken by a few sharp blows and will readily disintegrate so that it can easily be blown out of the casting.

The nature of expanded perlite, which is a new product, is such that gases produced when and as the metals, above mentioned, fill the mould are readily absorbed directly into the core body, or conveyed thru the core to a. place of disposal. Core venting is not necessary, and castings made show no tendency toward the pockets.

The binder specified, however, is best suited to the use here contemplated, and while the amount mixed in with the perlite is not critical, it should not ordinarily exceed ten (10) percent. Any greater amount is wasteful and unnecessary.'

The term resin" or natural resin as used herein is intended to mean the dry sap of pine trees, or the like, whether in a fresh state or after treatment by heat, such as rosin. The expression is used to distinguish this substance from artificial or synthetic resin.

In view of the foregoing, I wish to be limited only by the following claims:

I, claim:

1. A core forming composition for aluminum casting molds consisting of to percent classified expanded perlite and 10-5 percent of a binder composed of approximately 11 parts rosin, 40 parts synthetic urea-formaldehyde resin, .and 49 parts siliceous clay, by weight.

emo:

2. The method or making a mold core for casting aluminum. and the like, consistin: in

mixing about 95 percent expanded periite granules with percent binder composed of natural resin 11 parts, synthetic urea-formaldehyde resin 40 parts, and siliceous clay 49 parts, and adding sufilclent :water to make a clinging mix; then baking the resultant composition until dehydrated and until the binder has carbonized.

3. A core form for molds for casting aluminum and the like, composed of expanded perlite 90-95 percent and a carbonizable organic binder to maintain the shape of the core -5 percent, said binder being composed of natural resin 11 parts, synthetic urea-formaldehyde resin parts. and clay 49 parts, by weight.

4. A core forming composition for aluminum mold cores consisting of to percent classifled expanded perlite, together with 10 to '5 percent of a binder composed 01' 11 parts pine resin, 40 parts synthetic urea-formaldehyde resin, and 49 parts silicious 0188. by weight.

EDWARD S. ADAMS.

nmnnncns crrnn The following references are oi record in the tile 01 this patent:

UNITED STATES PATENTS Number Name Date 2,183,424 Clark Dec. 12, 1939 2,203,471 Ray June 4, 1940 2,322,638 Kleeman June 22, 1943 2,381,735 Gantz Aug. 7, 1945 1 2,388,060 Hicks Oct. 30, 1945 2,401,760 Heyroth June 11, 1946 2,431,884 Neuschotz Dec. 2, 1947 I FOREIGN PATENTS I Number Country Date 1 303,858 Great Britain Nov. 21, 1929 OTHER REFERENCES "Thermal Insulation i'rom Pei-lite, Chem. b Metallurgical Ens. vol. 52, July 1945, pp. 140, 142. 

